How can immunity be acquired

The antibody and antigen fit tightly together, like pieces of a jigsaw puzzle. Sometimes an antibody can attach to other antigens if the antigens closely resemble the antigen that the antibody was formed to recognize and attach to.

Variable part: This part varies from antibody to antibody, depending on which antigen the antibody targets. The antigen attaches to the variable part. This part is the same within each class. This part is the same within each class and determines the function of the antibody.

An antibody can switch its constant part and become a different class, but its variable part does not change. Thus, it can always recognize the specific antigen that it was formed to attach to.

This class of antibody is produced when a particular antigen such as an antigen of an infectious microorganism is encountered for the first time. The response triggered by the first encounter with an antigen is the primary immune response.

IgM then attaches to the antigen, activating the complement system, and thus makes the microorganism easier to ingest. IgG, the most prevalent class of antibody, is produced when a particular antigen is encountered again. More antibody is produced in this response called the secondary immune response than in the primary immune response.

The secondary immune response is also faster and the antibodies produced—mainly IgG—are more effective. IgG is present in the bloodstream and tissues.

It is the only class of antibody that crosses the placenta from mother to fetus. Also, IgG is the most common class of antibody used in treatment. For example, immune globulin antibodies obtained from the blood of people with a normal immune system consists mainly of IgG. Immune globulin is used to treat some immunodeficiency disorders Overview of Immunodeficiency Disorders Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual.

These antibodies help defend against the invasion of microorganisms through body surfaces lined with a mucous membrane, including those of the nose, eyes, lungs, and digestive tract. Colostrum the fluid produced by the breasts during the first few days after delivery, before breast milk is produced. These antibodies trigger immediate allergic reactions Overview of Allergic Reactions Allergic reactions hypersensitivity reactions are inappropriate responses of the immune system to a normally harmless substance.

Usually, allergies make people sneeze; the eyes water and itch IgE binds to basophils Basophils One of the body's lines of defense immune system involves white blood cells leukocytes that travel through the bloodstream and into tissues, searching for and attacking microorganisms and When basophils or mast cells with IgE bound to them encounter allergens antigens that cause allergic reactions , they release substances such as histamine that cause inflammation and damage surrounding tissues.

Thus, IgE is the only class of antibody that often seems to do more harm than good. However, IgE helps defend against certain parasitic infections that are common in some developing countries. Small amounts of IgE are present in the bloodstream and mucus of the digestive system. These amounts are higher in people with asthma, hay fever, other allergic disorders, or parasitic infections.

Small amounts of these antibodies are present in the bloodstream. Their function in the bloodstream, if any, is not well understood. Some microorganisms are directly recognized, ingested, and destroyed by cells that ingest these invaders phagocytes , such as neutrophils and macrophages. However, phagocytes cannot directly recognize certain bacteria because the bacteria are enclosed in a capsule. In these cases, B cells have to help phagocytes with recognition. The antibodies attach to the capsule.

When the body is exposed to the pathogen for a second time, the immune response is more robust, quickly addressing the disease agent. Immunity does not happen immediately upon disease exposure. It can take days or weeks after the first exposure for active immunity to develop.

But once it does so, the protection can last an entire lifetime. Active immunity can occur in one of two ways: naturally or via an immunization. Natural immunity is created when a person becomes infected by a disease. Take, for instance, someone who becomes infected with chickenpox. After the initial infection, the body builds immunity against the disease.

This natural active immunity is why people who catch chicken pox are immune for many decades against the disease. Also known as artificial active immunity, a person can build a resistance to a disease following an immunization. An immunization is defined as the process by which someone becomes protected against a specific disease via the administration of a vaccine.

Vaccines use a weakened or dead form of a disease to stimulate an immune response. Rare Cancers of Childhood Treatment. Childhood Cancer Genomics. Study Findings. Metastatic Cancer Research. Intramural Research. Extramural Research. Cancer Research Workforce.

Partners in Cancer Research. What Are Cancer Research Studies. Research Studies. Get Involved. Cancer Biology Research. Cancer Genomics Research. Research on Causes of Cancer. Cancer Prevention Research. Cancer Treatment Research. Cancer Health Disparities. Childhood Cancers Research. Global Cancer Research.

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Biomedical Citizen Science. Director's Message. Budget Proposal. Stories of Cancer Research. Driving Discovery. Antibodies are proteins produced by the body to neutralize or destroy toxins or disease-carrying organisms. Antibodies are disease-specific. For example, measles antibody will protect a person who is exposed to measles disease but will have no effect if he or she is exposed to mumps.

Active Immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Active immunity can be acquired through natural immunity or vaccine-induced immunity.